Silver halide photographic elements utilizing four-equivalent 5-pyrazolone magenta-dye-forming couplers are well known. Processing of these materials requires a stabilization step, usually employing a formaldehyde reagent, in which unreacted coupler is converted to an inert form that cannot initiate magenta dye fade.
It is also well known to use two-equivalent 5-pyrazolone magenta-dye-forming couplers which are advantageous because of their increased efficiency. Moreover, the two-equivalent 5-pyrazolone magenta-dye-forming couplers do not require the stabilization step and thus are environmentally advantageous alternatives to the four-equivalent couplers. However, the known two-equivalent 5-pyrazolone magenta-dye-forming couplers are generally too active, giving densities and granularities that are unacceptably high for use in state-of-the-art reversal film systems. This is particularly true when using low pH developers, for example, developers with a pH of less than 11.7.
Two-equivalent 5-pyrazolone magenta-dye-forming couplers known to the art typically incorporate ballast moieties that are primarily designed to prevent diffusion through the layers of the photographic element in which they are incorporated. Examples of such two-equivalent 5-pyrazolone magenta-dye-forming couplers are those described in U.S. Pat. No. 4,076,533 in which the coupling-off group is a triazole, U.S. Pat. No. 4,241,168 in which the coupling-off group is a 5-membered heterocycle, and U.S. Pat. No. 4,310,619 in which the coupling-off group is a substituted pyrazole. In these couplers, the ballast moieties comprise derivatives of anilino, benzamido, alkyl, arylureido or acylamino groups. The result is coupling activities, densities and granularities that are undesirably high.
It is toward the objective of providing novel two-equivalent 5-pyrazolone magenta-dye-forming couplers comprising activity-modifying ballasting groups which render them useful in state-of-the-art reversal film systems that the present invention is directed.